Fluid dispensing systems, for dispensing liquid or viscous materials, have become an integral part of the electronics manufacturing process for depositing underfill, encapsulants, solder fluxes, surface mount adhesives, conformal coatings, and other viscous materials onto a substrate, such as a printed circuit board. One type of fluid dispensing system operates by forcing a measured quantity of the fluid to be deposited through an aperture, or nozzle, to generate one or more droplets of the fluid that release from the nozzle without wetting the substrate and are deposited on the substrate. Fluid dispensing systems of this type, which are commonly known as jetting dispensers, typically include a replaceable nozzle that is coupled to a fluid applicator. The applicator includes a fluid chamber and a valve that work cooperatively to provide the forced quantity of fluid to the nozzle. To allow fluid to be dispensed in selected locations on the substrate, the applicator is typically coupled to a fluid dispensing machine by an X-Y positioner, although systems may also use mechanisms that move the substrate relative to the applicator. A system controller is coupled to the X-Y positioner and applicator valve, and provides a means of controlling the deposition of fluids on the substrate by selectively activating the X-Y positioner and the valve.
Typically, the valve includes an elongated member, or needle, with a tip configured to selectively engage a valve seat. During a jetting operation, the needle is moved relative to the valve seat by a driving mechanism. Contact between the tip of the needle and the valve seat seals off a discharge passage in the valve seat from the fluid chamber, which is supplied with fluid material under pressure. To dispense droplets of the fluid material, the needle is retracted from contact with the valve seat to allow a finite amount of the fluid material to flow through the newly formed gap and into the discharge passage. The tip of the needle is then moved rapidly toward the valve seat to close the gap, which generates pressure that accelerates the finite amount of fluid material through the discharge passage and causes a droplet of the material to be ejected, or jetted, from an outlet of the discharge passage.
The fluid dispensing machine is configured to provide controlled movements of the applicator above the substrate as the fluid material is jetted to land on an intended application area of the substrate. By rapidly jetting the material “on the fly” (i.e., while the jetting device is in motion), the dispensed droplets may be joined to form a continuous line or other pattern. Fluid dispensing machines with applicators may therefore be easily programmed to dispense a desired pattern of droplets of fluid material. This versatility has made jetting fluid dispensing systems suitable for a wide variety of applications in the electronics industry. For example, underfill material can be applied using a jetting dispenser to dispense fluid material proximate to one or more edges of the chip, with the material then flowing under the chip by capillary action. To allow the applicator to be adapted to different fluid dispensing operations, the nozzle is typically detachable from the applicator so that a nozzle can be selected and utilized which has the dispensing characteristics necessary for the desired dispensing operation or fluid type.
During a normal production run, the valve seat may be subjected to several million operation cycles. Over time, repeated contact between the valve needle and valve seat will cause valve seat to wear, altering the dimensions of the discharge passage. These changes in the discharge passage dimensions tend to alter the dispensing characteristics of the nozzle. In addition, the fluid may erode the nozzle discharge passage, further altering the shape, size, and uniformity of the droplets deposited by the applicator. These changes in the dispensing characteristics of the nozzle depend not only on the number of operation cycles, but also on the materials used to construct the valve seat, and the types of fluids being dispensed. For example, depositing fluids that have abrasive characteristics will typically cause the nozzle to wear out more quickly than depositing non-abrasive fluids. Likewise, a nozzle with a ceramic valve seat will typically have a different life expectancy than a nozzle with a metal valve seat. Thus, to maintain the desired fluid dispensing characteristics of the dispensing system, the nozzle must occasionally be replaced, with the required replacement time depending on the operational history of the nozzle.
Determining the operational history of a jetting dispenser may be difficult, however, because the nozzle may have been moved between different fluid dispensing machines over its lifetime, as well as used to dispense various fluids. Nozzles may therefore be replaced prematurely, or left in service too long, because system operators have lost track of the operational history of the nozzle. Nozzles that have been used to dispense one type of fluid may also be inadvertently attached to a fluid dispensing machine used to deposit a different, incompatible type of fluid. These errors may result in unnecessary expenses from replacing nozzles that have not yet worn out and from substrates that must be discarded or recycled due to improper fluid deposition.
Thus, there is a need for improved devices, systems, and methods of tracking the configuration or operational history of nozzles, such as jetting dispenser nozzles, and for determining when nozzles have reached the end of their operational lifetimes.